Gas generating device



May 2, 1961 P. B. CAMPBELL GAS GENERATING DEVICE Filed Jul 9, 1959INVENTOR PHILLIP B. CAMPBELL GAS GENERATING DEVICE Phillip B. Campbell,Kansas City, Mo., assignor to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Filed July 9, 1959, ser.N 826,043 -7 Claims. c 60-3914) This invention relates to gas generatingdevices, more particularly togas generating devices wherein acombustible charge is disposed within a housing and ignited to provide aflow of hot gaseous combustion products for an interval of time, and hasfor an object to provide an improved device of this character.

It is a further object of the invention to provide a gas generatingdevice of the above type, wherein 'the hot gaseous products formed uponignition of a primary combustible charge are directed through a firstpassageway for utilization in one portionof a reaction engine and,wherein after a preselected period of time, the hot gaseous products aredirected through a secondary passageway 'for utilization in anotherportion of the reaction engine, a and including means providing a secondcombustible charge for initially blocking the secondary passageway fl dStates Patent but unblocking the secondary passageway when consumed.

Briefly, the invention provides a gas generating device comprising apressure tighthousing having a primary and a secondary outlet, a primarycombustible charge disposed within the housing, a secondary combustiblecharge of solid form disposed in and blocking the secondary passageway,and means forigniting the primary and secondary charges The secondarycharge is disposed in a manner to be ignited concomitantly with theprimary charge. Accordingly, upon ignition of the primary charge, alarge volume of hot gaseous products of combustion are rapidly generatedand directed from the housing through the primary passageway.

The secondary charge is also ignited at the same time as the primarycharge. After the secondary charge is completely consumed, it unblocksthe secondary passageway and flow of the hot gaseous productstherethrough is initiated. The proper selection of the material andaxial length of the secondary charge consistent with the time requiredfor complete consummation of the secondary charge may be predeterminedwith a high degree of accuracy, so thatthe time delay between initiationof gas flow through the primary passageway and the secondary passagewaymay be accurately predetermined.

Although the device mentioned above may conceivably have wide utility,it is especially suited for controlling the starting of a gas turbineengine. As well known in the art, gas turbine engines arenotself-starting and their rotors must be driven by external means to acritical speed necessary for self-sustaining operation of the engine.Many devices have heretofore been proposed for accelerating the turbinerotor to the critical starting speed. However, after the rotor isaccelerated to the critical speed by such prior art devices, ignition ofthe fuel is attained by a suitable, but highly complex engine control.

With this invention, both the rotor acceleration step and the fuelignition step are attained in an exceedingly simple, yet highlyreliable, manner, by connecting the primary gas passageway to theturbine rotor blading to c 2,982,095 Patented May2, 196-1 provide motivegases for acceleration purposes, and by subsequently unblocking thesecondary gas passageway to the fuel combustion section for ignition.

Accordingly, a more specific object of the invention is to provide anauxiliary'gas generating device-including a primary combustible chargefor providing hot gaseous products of combustion for initially crankinga gas turbine engine and bringing the rotor of the engine to a speed atwhich the engine may be fired to become selfsustaining, and having asecondary passageway for delivering a portion of the hot gaseousproducts to the fuel combustion apparatus of the engine for ignition,after the rotor of the engine has attained the above speed.

The foregoing and other objects are effected by the invention as will beapparent from the following description and claims taken in connectionwith the accompanying' drawing, forming a part of this application, inwhich:

Fig. 1 is a longitudinal elevational view of an aviation turbojet engineequipped with a gas generating device formed in accordance with theinvention;

Fig. 2 is a sectional view, on a larger scale, taken on lines IIII ofFig. 1;

Fig. 3 is a view similar to Fig. 2, but enlarged to show further detailsof the gas generating device;

Fig. 4 is an enlarged transverse sectional view taken on lines IVIV ofFig. 2; and,

Fig. 5 is a fragmentary sectional View taken on line V-V of Fig. 3.

Referring to the drawing in detail, in Fig. 1 there is shown an aviationturbojet engine 10 equipped with a gas generating device 12 formed inaccordance with the invention. The turbojet engine 10 forms no part ofthe invention and may be of any suitable type. Accordingly, it has beenshown in somewhat schematic form. As well known in the art, the enginecomprises a tubular outer shell or housing 13 defining a forwardlydirected air intake opening 14- and a rearwardly directed exhaust nozzle15. Within the shell 13 there are disposed in the following order, anair compressor section 16 including a bladed rotor 17, an annular airpassageway 18 extending from the outlet of the compressor section 16 tothe inlet of a gas turbine section 19 having a bladed rotor 20, and fuelcombustion structure 22 disposed within the air passageway 18. Theturbine rotor 20 is drivingly connected to the compressor rotor 17 by asuitable shaft.

The fuel combustion structure 22'includes a foraminous fuel combustor 23of annular shape provided with a plurality of fuel injection nozzles 24connected by a suitable manifold 25 to a source of fuel supply (notshown).

As is well known in the art, engines of the above type are notself-starting and must be provided with means for cranking the rotorstructure 17 and 20 to a sufficiently high speed before the combustiblefuel and air mixture formed in the fuel combustor 23 is ignited toprovide hot motive gases for driving the turbine rotor 20. This speedmay be on the order of about 40 percent of the maximum rated speed ofthe engine. For example, in an engine which has a maximum rotationalspeed of 10,000 r.p.m., the rotors must be initially rotated by asupplementary source of power to a speed of about 4,000 rpm. before thefuel combustion structure 22 may be fired. Many devices have heretoforebeen utilized in the prior art to initially rotate the rotor structureto the speed at which self-sustained operation may be obtained by theengine. However, after initial rotation to the speed at whichself-sustained operation may be obtained, it has heretofore beennecessary to ignite the fuel and air mixture by separately actuatedignition means.

In accordance with the invention, the gas generating device 12 comprisesa pressure tight tubular shell or housing 27' of elongated shape havinga nozzle structure 28 attached to one end thereof and having an endclosure cap 29 disposed at the opposite end.

The nozzle structure 28, as best shown in Figs. 2, 3 and 4, has aplurality of exit nozzles 30 extending through the engine shell 13 andregistering with an annular row of lant charge 34 is snugly receivedwithin the housing 27 and is preferably of discrete form with itslongitudinal bore 33 preferably formed with a plurality of radiallyoutwardly extending surface portions 35 to provide a large burning area.In the illustrated embodiment, the surface portions 35 impart agenerally star-shaped cross section to the bore, as best shown in Figs.4 and 5.

An ignitor squib 36 is threadedly received in the end cap 29 and extendstherethrough into the longitudinal bore 33, as best shown in Fig. 3. Thesquib 36, as well known in the art, may comprise a casing 37 of tubularshape having a readily ignitable material 38 contained therein anddisposed in encompassing relation with an electrical filament 39 whichmay be heated to incandescence by directing an electrical currenttherethrough from any suitable electrical supply, for example, a battery40, when a switch 41 is moved to the circuit making position. The

' casing 37 is provided with .a plurality of outlets 42 disposed inregistry with the bore 33.

Adjacent the forward end, that is the end adjacent the squib 36, thereis provided a tubular member 43 defining a radially outwardly extendingpassageway 44 and connected to the interior of the fuel combustor 23 bya suitable conduit 45, as shown in Fig. 3. The conduit 45 is tightlyattached to the housing 27 at one end and to the engine shell 13adjacent its opposite end by suitable fittings 46 and 47, respectively.The conduit 45 further extends through the air passageway 18 and has itsoutlet end 48 snugly received in the wall structure of the fuelcombustor 23.

Within the radially extending passageway 44, there is provided a solidpropellant plug or charge 49 of discrete form which is snugly receivedtherein and held in position by the fitting 46 in such a manner that itblocks gas flow therethrough. The plug 49 has an exposed end surfaceportion 50 disposed adjacent the bore 33 and readily ignitable.

The gas generating device 12, when ignited, automatically provides thecranking or starting impulse to the rotors 17 and 20 and acceleration ofthe same to the starting speed, and subsequently automatically ignitesthe combustible fuel and air mixture in the combustor 23.

To initiate the cranking operation of the engine, the switch 41 is movedto the circuit making position, thereby connecting the filament 39 ofthe squib to the electrical power source 40. The filament 39 is thusrapidly heated to incandescence and causes ignition of the charge 38 inthe squib. The ensuing highly heated gaseous products of combustion andincandescent particles are violently ejected through the squib outlets42 into the bore 33 of the primary propellant charge, thereby causingignition of the same along the surfaces 35 of the bore. Hot gaseousproducts of combustion are thereby formed at a high rate and pressureand ejected in a steady stream through the passageway 32 and nozzles 30in the nozzle structure 28 against the turbine blades 31 with sufficientforce to drive the turbine rotor 20 with a rapidly accelerating effect.

Since the turbine rotor 20 is connected to the compressor rotor 17, airis drawn into the engine through the air intake opening 14, pressurizedas it flows through the compressor section 16 and thence directedthrough the passageway 18 into the fuel combustor 23, wherein it ismixed with fuel being admitted by injector nozzles 24 to provide acombustible fuel and'air mixture.

Concomitantly with ignition of the primary propellant charge 34, thepropellant plug 49 is ignited. When the propellant plug 49 issubstantially totally consumed, the hot gaseous products generated bythe primary propellant charge are bled through the conduit 45 and intothe combustor 23 to ignite the fuel and air mixture therein.Accordingly, the engine is thus automatically fired when the speed ofthe rotors is sufiicient to permit self-sustaining operation and theprimary charge is subsequently consumed. Thereafter the engine willcontinue to operate without further assistance of the gaseous productsfrom the gas producing device 12.

The gas producing device 12 may be attached to the engine shell 13 inany suitable manner and, since it is relatively small, presents only asmall weight penalty on the engine during flight. Accordingly, it may beleft attached to the engine after the engine is started, if so desired.

The propellant plug 49 is preferably of considerably less mass than theprimary charge 34, but may be of any suitable propellant material andmay be of any crosssectional shape. However, it is desirable to form theplug 49 of sufficient length to provide a predetermined time intervalbetween the initial ignition of the main propellant charge and completeconsumption of the plug, since the burning rate of the plug 49 is adirect function of its axial length.

Further, the axial length and the burning rate of the plug 49 must be ofsuch a nature that the passageway 44 is opened before the mainpropellant is completely consumed, so that sufficient hot gaseousproducts of combustion may be directed through the conduit 45 into thecombustor 23 to eifect ignition of the fuel and air mixture.

The gas generating device 12 may be employed repeatedly by replacing theconsumed squib 36 and inserting another primary charge 34 and plug 49.

It will now be seen that the invention provides a gas generating devicewhich combines several functions in a highly simple and straightforwardmanner. More par; ticularly, with the invention, the gaseous products ofcombustion formed by the main propellant charge are first directedthrough one outlet passageway to energize one portion of the engine andsubsequently, after a delayed time interval, are ejected through anotherpassageway to assist or initiate a second function of the engine.Although in the embodiment shown the gas generating device is employedin conjunction with a turbojet engine and the starting thereof, theinvention may be provided in other apparatus wherein two successive andproperly timed functions are required.

Although the invention has considerably wide utility, it is particularlysuited for starting a guided missile wherein such starting is effectedby remote control. For example, the invention is highly advantageous foruse in an airborne missile which may be carried aloft by a motheraircraft and launched therefrom after the desired altitude is attained.

While the invention has been shown in but one form, it will be obviousto those skilled in the art that it is not so limited, but issusceptible of various changes and modifications without departing fromthe spirit thereof.

What is claimed is:

1. A gas generating device comprising a housing, a primary combustiblecharge disposed within said housing, means defining a primary gaspassageway extending outwardly from said housing and communicating withsaid charge, means defining a secondary gas passageway extendingoutwardly from said housing and communicating with said charge, a secondcombustible charge disposed in blocking relation with said secondpassageway, and means for concomitantly igniting said primary charge andsaid second charge, said primary charge forming gaseous combustionproducts, said second combustible charge initially blocking flow of saidgaseous combustion products through' said second passageway but-beingcon- 2. A gas generating device comprising a housing, a

primary combustible charge of discrete form disposed within saidhousing,said charge having an opening, means for igniting said primary chargeand initiating generation of gaseous combustion products, means defininga primary gas passageway extending outwardly from said housing andcommunicating with the opening in said charge, means defining asecondary gas passageway extending outwardly from said housing andcommunicating with the opening in said charge, and a second combustiblecharge of discrete form disposed in said second passageway, said secondcharge being disposed adjacent said primary charge and being ignitablejointly therewith, said second combustible charge initially blockingflow of gaseous combustion products through said second passageway butbeing consumable within a predetermined length of time after ignition ofsaid primary charge by said igniting means to unblock said secondpassageway and initiate flow of said combustion products therethrough.

3. A gas generating device comprising a housing, a primary combustiblecharge of discrete form disposed within said housing, means defining aprimary gas passageway extending outwardly from said housing andcommunicating with said charge, means defining a secondary gaspassageway extending outwardly from said housing and communicating withsaid charge, a second combustible charge of discrete form disposed insaid second passageway, and means for concomitantly igniting saidprimary and secondary charges, said primary charge forming gaseouscombustion products upon ignition, said second combustible chargeinitially blocking flow of said gaseous combustion products through saidsecond passageway but being consumable within a predetermined period oftime after ignition to unblock said second passageway and initiate flowof said combustion products therethrough, said primary charge having alonger burning period than said secondary charge.

4. A gas generating device comprising a housing, a primary combustiblecharge of solid form enclosed within said housing, said charge having anaxial passage extending from end-to-end defined by an internal surfaceportion of said charge, means disposed in communication surface portionof said charge, thereby to initiate formation of gaseous combustionproducts, means defining a primary gas ejection passageway communicatingwith said axial passage and extending outwardly from said housing, meansdefining a secondary gas ejection passageway communicating with saidaxial passageway and extending outwardly from said housing, and asecondary charge of combustible solid material disposed in andobdurating said secondary passageway, said secondary charge having anend surface portion disposed adjacent said axial passage and ignitablesubstantially concomitantly with said primary charge, said secondarycharge being consumable within a predetermined period of time afterignition and of shorter duration than the consumption period of saidprimary charge, and initiating flow of said gaseous combustion productsthrough said secondary passageway after said predetermined period, saidsecondary charge being of smaller mass than said primary charge.

5. In a gas turbine power plant having a bladed turbine rotor, acompressor rotor connected thereto, and fuel combustion structure; thecombination therewith of an auxiliary hot gas generating devicecomprising a pressure tight housing, a primary charge of combustiblesolids enclosed within said housing, said charge having an internalsurface portion defining an elongated passage,

means disposed in communication with said passage for "igniting theinternal surface portion of said charge,

thereby to initiate formation of pressurized hot gaseous combustionproducts, means including a nozzle structure communlcating with saidelongated passageway for conducting said gaseous products from saidhousing to one of the rotors to effect initial rotation of said turbinerotor, means defining a secondary passageway communicating with saidelongated passageway for conducting said gaseous products from saidhousing to said combustion structure to effect ignition of the fuel insaid fuel combustion structure, and a secondary combustible chargedisposed in and blocking said secondary passageway, said secondarycharge being of predetermined axial length and having a surface portionin communication with said elongated passageway, said secondary chargebeing consumable within a predetermined time interval after ignition ofsaid primary charge and being effective to unblock said secondarypassageway and initiate flow thereto.

6. In a gas turbine power plant having a turbine rotor, an aircompressor rotor connected to said turbine rotor, and fuel combustionstructure interposed between said rotors for providing hot motive gasesto said turbine rotor; the combination therewith of an auxiliary hot gasgenerating device comprising a pressure tight housing, a primary chargeof combustible solids enclosed within said housing, said charge havingan internal surface portion defining an elongated passage, meansdisposed in communication with said passage for igniting the internalsurface portion of said charge, thereby to initiate forma tion ofpressurized hot gaseous combustion products, means including a'nozzlestructure communicating with said elongated passage for conducting saidgaseous products from said housing to one of the rotors to effectinitial rotation of said turbine rotor, means defining a secondarypassageway communicating with said elongated passage for conducting saidgaseous products from said housing to said fuel combustion structure toeffect ignition of the fuel in said fuel combustion structure, and asolid combustible plug disposed in and blocking said secondarypassageway, said plug being of predetermined axial length and having asurface portion in communication with said elongated passage, said plugbeing consumable within a predetermined time interval after ignition ofsaid primary charge to unblock said secondary passageway and initiateflow of said gaseous products therethrough.

7. In a gas turbine power plant having a bladed turbine rotor, acompressor rotor connected thereto and a fuel combustion structure forproviding hot motive gases to said turbine rotor; the combinationtherewith of an auxiliary hot gas generating device comprising anelongated pressure tight housing, a primary charge of combustible solidsenclosed within said housing, said charge having an internal surfaceportion defining an elongated central bore, means disposed incommunication with said bore for igniting the internal surface portionof said charge, thereby to initiate formation of pressurized hot gaseouscombustion products, means including a tubular nozzle membercommunicating with said bore, said nozzle member being disposed inregistry with said turbine rotor and being efiective to conduct saidgaseous products from said housing to eifect initial rotation of saidturbine rotor, means defining a secondary passageway communicating withsaid bore and extending radially therefrom, said last mentioned meansfurther including a conduit disposed in communication with said fuelcornbustion structure and being effective to conduct said gaseousproducts from said housing to effect ignition of the fuel in said fuelcombustion structure, and a solid combustible plug disposed in andblocking said secondary passageway, said plug being of predeterminedaxial 7 T8 length and having a surface portion in communication 1References Cited inthe file of this patent 2155312225? aizi 'g i ta bl jc fin i 31 11 5%;225213 UNITED STATES PATENTS 1 11 1 charge, said plugbeing consumable withinapredeter- 'gg Wheeler et 1949 mined timeintervalafter ignition and being effective :5 37269 71950 to unblocksaid secondary passageway and initiate flow .of said gaseous productstherethrough.

2,850,976 Seifert Sept. 9, 1958

